Automobile manufacturers are under increasing pressure to improve the fuel efficiency of vehicles. One means of improving fuel efficiency is utilizing transmissions with more speed ratios, thereby operating the engine closer to its most efficient speed at various vehicle speeds. Generally, increasing the number of available speed ratios requires increasing the number of gear sets and clutches and consequently making the transmission physically longer. However, automobile manufacturers are also under pressure to reduce the width of the engine compartment. For transverse mounted powertrains, this severely constrains the ability to use a longer transmission.
Four wheel drive vehicles based on longitudinal powertrains utilize a transfer case behind the transmission. Many transfer cases include a driver selected low range mode which provides additional speed reduction. This low range mode is useful when additional torque is needed or when improved vehicle speed control is needed. Vehicles with transverse powertrains do not use a transfer case and therefore have not offered drivers a low range mode.